Umbilical Cord Blood
The umbilical cord is the cord that connects the fetus to the maternal placenta, providing nutrients and removing wastes. The umbilical cord is a cordlike structure about 22 in. (56 cm) long in a pregnant woman, extending from the abdominal wall of the fetus to the placenta.
The main function of the umbilical cord is to carry nourishment and oxygen from the placenta to the fetus and return waste products to the placenta from the fetus. The umbilical cord achieves this function by consisting of an extension of the membrane covering the fetus that encloses a mucoid jelly through which one vein carries oxygenated blood and two arteries carry un-oxygenated blood.
Blood is carried from the fetus along the umbilical cord and into the placenta. Here it is brought close to the mother's blood. Oxygen, nutrients, and antibodies from the mother diffuse into the fetal blood and waste materials from the fetus pass into the mother's blood, via the two un-oxygenated arteries. The fetal blood, which has been enriched with nutrients, oxygenated, and cleaned of waste, is then carried back to the fetus by the vein that carries oxygenated blood in the umbilical cord.
After birth, the cord is clamped off and cut. The stump of the cord that is left attached to the infant, after the cord is cut off, withers and drops off, leaving the scar known as the navel.
Sometimes the cord is abnormal in length and may break prematurely or form loops or knots, which may asphyxiate the fetus by depriving it of oxygen.
Where Do Stem Cells Come From?
Because umbilical cord blood is especially rich in stem cells (cells that give rise to red blood cells and lymphocytes) some parents choose to save it in special cord blood banks in case of future need as a transplant alternative to bone marrow. Studies have shown that even people not related to the donor (genetically mismatched) can benefit from transplants of umbilical cord blood in combating leukemia and other cancers.